Re: [PATCH v6 21/40] arm_mpam: resctrl: Hide CDP emulation behind CONFIG_EXPERT

[Gavin Shan]

On 3/14/26 12:45 AM, Ben Horgan wrote:
> When CDP is not enabled, the 'rmid_entry's in the limbo list,
> rmid_busy_llc, map directly to a (PARTID,PMG) pair and when CDP is enabled
> the mapping is to two different pairs. As the limbo list is reused between
> mounts and CDP disabled on unmount this can lead to stale mapping and the
> limbo handler will then make monitor reads with potentially out of range
> PARTID. This may then cause an MPAM error interrupt and the driver will
> disable MPAM.
>
> No problems are expected if you just mount the resctrl file system
> once with CDP enabled and never unmount it. Hide CDP emulation behind
> CONFIG_EXPERT to protect the unwary.
>
> Signed-off-by: Ben Horgan <ben.horgan@xxxxxxx>
> ---
> Adding this ugliness in the hope of avoiding patch churn and extra
> reviewer work. I am looking into the resctrl changes needed to fix this.
> ---
>   drivers/resctrl/mpam_resctrl.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>